Permanent magnet synchronous rotating electric machine and rotor core

ABSTRACT

A permanent magnet synchronous rotating electric machine includes a rotor and a stator. The rotor includes a first hole, a second hole, a first magnet, and a second magnet. The second hole is provided on an opposite side with respect to a center line extending along a radial direction of the rotor. The first magnet is provided in the first hole and extends along a first longitudinal axis inclined at a first acute angle with respect to the center line. The second magnet is provided in the second hole and extends along a second longitudinal axis inclined at a second acute angle with respect to the center line. The second acute angle is smaller than the first acute angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of the U.S. patentapplication Ser. No. 13/183,437, filed Jul. 15, 2011, which is acontinuation application of the U.S. patent application Ser. No.11/960,773, filed Dec. 20, 2007, which claims priority to JapanesePatent Application No. 2007-072140 filed Mar. 20, 2007. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a permanent magnet synchronous rotatingelectric machine and a rotor core.

2. Discussion of the Background

Recently, from viewpoints of prevention of global warming and resourceconservation, duties to be performed by a vehicle such as a hybrid car,and an industrial power saving machine are becoming very important. Inorder to perform the duties, it is necessary to reduce CO₂-discharge,and improve the amount of energy consumption and efficiency.

For such the vehicle such as the hybrid car or the industrial powersaving machine, a permanent magnet type synchronous rotating electricmachine is required, which has characteristics that high output andhigh-speed rotation are possible, reliability is high and efficiency isgood, rotation speed is variable, and controllability is good. As arotating electric machine satisfying this condition, there is asynchronous motor in which a permanent magnet is included in a rotor,that is, an interior permanent magnet (IPM) motor. Since this motorproviding size reduction and weight reduction are realized, the range ofits use in the field of the industrial power saving machine isincreasing. For example, the motor is applied also to a crane, a windingmachine, an elevator, an elevator of a multi-level parking zone, acompressor or a blower for wind or water power, a fluidmachine such as apump, and a processing machine including mainly a semiconductormanufacturing member or a machine tool. In the present embodiment, IPMmotor will be mainly described

FIG. 6 is a front view of an electromagnetic steel plate forming memberblanked to mold a rotor core in a first related art.

In FIG. 6, an electromagnetic steel plate forming member 35 is composedof a thin disc-shaped electromagnetic steel plate for forming a rotorcore. In this electromagnetic steel plate forming member 35, a magnetichole 31 for inserting therein a permanent magnet is provided per polewhen the rotor is formed. An outer bridge 32 is formed between thismagnet hole 31 and a circumferential surface of the rotor. When theplural electromagnetic steel plate forming member 35 are laminated inthe block shape, an electromagnetic steel plate laminator (rotor core 34in FIG. 7) is manufactured (refer to, for example, JP-A-2006-211826,Specification P.4, and FIGS. 1 to 3 and Toyo Denki Technical Report No.111, 2005-3, P.13 to P.21).

Next, the operational principle of the interior permanent magnet motorwill be described.

FIG. 7 is a front sectional view of a main part of an interior permanentmagnet motor to which the rotor in the first related art is applied. Inthe shown motor, the number of magnetic poles of permanent magnets ofthe rotor is six poles, and the number of magnetic poles of salientpoles of a stator (the same number as the number of slots) is 36 pieces.

In FIG. 7, regarding the operation of the motor, in the rotor 30 inwhich a permanent magnet 33 is inserted into the interior of a rotorcore 34, the gap flux density becomes high in a q-axis constituting amagnetic convex portion which is small in magnetic resistance, and thegap flux density becomes low in a d-axis constituting a magnetic concaveportion which is large in magnetic resistance. By such the saliency ofthe rotor 30, the following relation is produced: Lq>Ld, when Lq isq-axis inductance and Ld is d-axis inductance. Therefore, reluctancetorque produced by change in flux density in addition to magnet torquemay be used, so that more increase in efficiency may be expected. Themagnet torque generates by a magnetic attraction force and a magneticrepulsion force between a magnetic field by the permanent magnet 33 ofthe rotor 30 and a rotating magnetic field by a stator winding housed(not-shown) in a slot 42 in a stator core 41 of the stator 40. Thereluctance torque generates by attraction of the salient pole portion ofthe rotor 30 to the rotating magnetic field by the stator winding (notshown).

Next, a second related art will be described with reference to FIG. 8.

FIG. 8 is a front view of an electromagnetic steel plate forming memberblanked to mold a rotor core in the second related art (refer to, forexample,

-   JP-A-2005-039963, Specification P.4 to P.6, and FIGS. 1 and 2,-   JP-A-2005-057958, Specification P.4 to P.7, and FIGS. 1 and 5,-   JP-A-2005-130604, Specification P.8, and FIG. 1,-   JP-A-2005-160133, Specification P.8, and FIG. 1,-   JP-A-2002-112513, Specification P.5, and FIGS. 1 and 3, and-   JP-A-2006-254629, Specification P.7 and P.8, and FIG. 4.)

In FIG. 8, an electromagnetic steel plate forming member 50 is composedof a thin disc-shaped electromagnetic steel plate for forming a rotorcore. In this electromagnetic steel plate forming member 50, two magnetholes 52 and 53 are provided in the V-shape so that two magnets per poleare inserted on the rotor outer diameter side symmetrically with respectto radial pole pitch lines provided at a predetermined pole pitch angle,when a rotor is formed. An outer bridge 54 is formed between the outerend portion of the magnet holes 52, 53 and a circumferential surface ofthe rotor. Further, in the electromagnetic steel plate forming member50, a center bridge 51 is provided between the magnet holes 52 and 53.When the plural electromagnetic steel plate forming member 50 arelaminated in the block shape, an electromagnetic steel plate laminator(rotor core 57 in FIG. 9) is manufactured.

Next, the operation will be described with reference to FIG. 9.

FIG. 9 is a front sectional view of a main part of an IPM motor to whichthe rotor in the second related art is applied, which showsschematically a positional relation of poles between a stator and arotor which generate optimum rotating torque. FIG. 10A and 10B arediagrams for explaining of the operation of the IPM motor in the secondrelated art. FIG. 10A is a schematic diagram showing the operation whenthe motor rotates normally, and FIG. 10B is a diagram showing a relationbetween a current phase which generates a rotating magnetic field of themotor and torques. The number of magnetic poles of permanent magnets ofthe rotor in the shown motor is eight poles, and the number of magneticpoles of salient poles of a stator (the same number as the number ofslots) is 48 pieces.

In FIGS. 9 and 10A, the IPM motor has a permanent magnet type rotor 50in which permanent magnets 55, 56 having the same size as the size ofmagnet holes 52, 53 are inserted into the magnet holes. In such theconstitution, a magnetic field by the permanent magnets 55, 56 embeddedin the interior of a rotor core 57 and a rotating magnetic field by astator winding housed (not-shown) in a slot 62 in a stator core 61 of astator 60 attract and repel each other, thereby to generate a magnettorque. Further, since the magnetic resistance in the direction of aq-axis orthogonal to the direction of a d-axis which is a magnet axisbecomes smaller than that in the d-axis direction, saliency structure isprovided. Therefore, a q-axis inductance Lq becomes larger than a d-axisinductance Ld, and reluctance torque generates by this saliency. InFIGS. 9 and 10A, the permanent magnets 55, 56 which are embedded in themagnet holes 52, 53 and arranged in the V-shape are isosceles.Therefore, a repulsion-boundary point of magnetic fluxes by thepermanent magnets in an outer iron core portion sandwiched between thetwo permanent magnets having the same size which are opposed to eachother in the same poles is located in the center of the outer iron coreportion of the rotor 50, and on a center line OC passing through acenter of the radial pole pitch lines OP.

In FIGS. 9 and 10A, though a force for giving rotary energy to the rotor50 is actually composed by strength of current flowing in the statorwinding (not shown) in the slot 62 and the like, its description issimplified here. Flux density distribution of the motor will bedescribed, paying attention to a pole located at 12 o'clock.

The d-axis repulsion-boundary point of the outer iron core portionsurrounded by the two permanent magnets 55, 56 of the same polarity islocated in the center of the surface of the rotor 50. In case that thepoles formed by the stator windings (not shown) in the slots 62 areshown as in FIGS. 9 and 10A, on the gap surface between the stator 60and the rotor 50, the left side with respect to the repulsion-boundarypoint on the line OC becomes an attraction part constructed so that thestator is the N-pole and the rotor is the S-pole, and the right sidewith respect to the repulsion-boundary point on the line OC becomes arepulsion part constructed so that both of the stator and the rotorbecome the S-pole. On the surface of the rotor 50, the attraction partbecomes dense in magnetic flux and the repulsion part becomes sparse inmagnetic flux. Therefore, magnet torque which is about to move the rotor50 from the side in which the magnetic flux is dense to the side inwhich the magnetic flux is sparse, that is, in the clockwise directionacts on the rotor 50. Further, the q-axis flux flows mainly in teeth 63of the stator 60 opposed to the salient poles.

In the description related to FIG. 10A, since attraction is producedbetween the magnetic fields by the permanent magnets 55, 56 of the rotor50 and the rotating magnetic fields by the stator windings (not shown)in the slots 62 and the d-axis salient pole portion of the rotor 50 isattracted to the rotating magnetic field by the stator winding (notshown) , the flux density in the oblique line portion becomesparticularly high. At this time, with respect to the S-pole component ofthe permanent magnets and the S-pole component by the stator windings(not shown) , the N-pole component by the windings is short. Therefore,the reluctance torque which is about to move the rotor 50 in a directionwhere the magnetic flux of the S-pole component is shortened, that is,in the clockwise direction acts on the rotor 50.

Here, as shown in FIG. 10B, the magnet torque which is produced by themagnetic attraction force and the magnetic repulsion force between themagnetic field by the magnet and the rotating magnetic field by thewinding shows a relation of a curve in the figure, and the reluctancetorque generated by the attraction of the salient pole portion of therotor to the rotating magnetic field by the winding shows a relation ofa curve in the figure. Hereby, by putting the magnet torque and thereluctance torque together, a torque shown by a thick solid line in thefigure may be generated.

However, in the second related art, in the outer iron core portionformed between the upper surface of the two permanent magnet insertionholes and the outer diameter of the rotor core, the q-axis flux byarmature reaction is easy to be saturated. Therefore, the reluctancetorque may not be utilized, so that it is difficult to obtain largetorque in the starting time or in abrupt change in load.

Further, as shown in the second related art, in the shape in which thetwo permanent magnets are arranged in the V-shape per pole, magneticanisotropy is stronger than that in the shape having flat arrangement ofthe permanent magnets as shown in the first related art. However, theanisotropy is not sufficiently used, and this shape in the secondrelated art does not attribute to improvement of motor efficiency in thelow-speed operation time and in the light-load operation time.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a permanent magnetsynchronous rotating electric machine includes a rotor and a stator. Therotor includes a first hole, a second hole, a first magnet, and a secondmagnet. The second hole is provided on an opposite side with respect toa center line extending along a radial direction of the rotor. The firstmagnet is provided in the first hole and extending along a firstlongitudinal axis inclined at a first acute angle with respect to thecenter line. The second magnet is provided in the second hole andextending along a second longitudinal axis inclined at a second acuteangle with respect to the center line. The second acute angle is smallerthan the first acute angle and is formed opposite to the first acuteangle with respect to the center line. An outer circumferential distancebetween a first radially outer end of the first magnet and a secondradially outer end of the second magnet is greater than an innercircumferential distance between a first radially inner end of the firstmagnet and a second radially inner end of the second magnet. The statorincludes a stator core and a stator winding provided to the stator core.The stator has a displacement point of magnetism to be generated by acurrent passing through the stator winding of the stator. Thedisplacement point is provided on an inner peripheral surface facing anouter peripheral surface of the rotor via a gap. The magnetism of therotor on the outer peripheral surface is different from the magnetism ofthe stator on the inner peripheral surface on a first side of the centerline when the displacement point is provided substantially on the centerline of the rotor. The magnetism of the rotor on the outer peripheralsurface is same as the magnetism of the stator on the inner peripheralsurface on a second side of the center line when the displacement pointis provided substantially on the center line of the rotor. The secondside is provided on an opposite side of the first side with respect tothe center line in the circumferential direction.

According to another aspect of the present invention, a permanent magnetsynchronous rotating electric machine includes a rotor and a stator. Therotor includes a first hole, a second hole, a first magnet, and a secondmagnet. The secondhole is provided on an opposite side with respect to acenter line extending along a radial direction of the rotor. The firstmagnet is provided in the first hole and extending along a firstlongitudinal axis inclined at a first acute angle with respect to thecenter line. The second magnet is provided in the second hole andextending along a second longitudinal axis inclined at a second acuteangle with respect to the center line. The second acute angle is smallerthan the first acute angle and is formed opposite to the first acuteangle with respect to the center line. An outer circumferential distancebetween a first radially outer end of the first magnet and a secondradially outer end of the second magnet is greater than an innercircumferential distance between a first radially inner end of the firstmagnet and a second radially inner end of the second magnet. The statorincludes a stator core and a stator winding. The stator core has aplurality of teeth. The stator winding is provided to the teeth. Thestator has a displacement point of magnetism to be generated by acurrent passing through the stator winding of the stator. The seconddisplacement point is provided on an inner peripheral surface facing anouter peripheral surface of the rotor via a gap. A d-axis is defined asa magnetic axis of a magnetic convex portion of the rotor. A q-axis isdefined as a salient pole of a magnetic concave portion of the stator.Substantially two of the teeth of the stator core are opposed to thesalient pole in which magnetic flux along the q-axis flows when thedisplacement point is provided substantially on the center line of therotor.

According to further aspect of the present invention, a rotor coreincludes an electromagnetic steel plate layered body, a first hole, asecond hole, a first magnet, and a second magnet. The electromagneticsteel plate layered body includes a first hole and a second hole. Thesecond hole is provided on an opposite side with respect to a centerline extending along a radial direction of the rotor. The first magnetis provided in the first hole and extending along a first longitudinalaxis inclined at a first acute angle with respect to the center line.The second magnet is provided in the second hole and extending along asecond longitudinal axis inclined at a second acute angle with respectto the center line. The second acute angle is formed opposite to thefirst acute angle with respect to the center line. An outercircumferential distance between a first radially outer end of the firstmagnet and a second radially outer end of the second magnet is greaterthan an inner circumferential distance between a first radially innerend of the first magnet and a second radially inner end of the secondmagnet. The second acute angle is smaller than the first acute angle sothat saturation of flux along q-axis is suppressed and reluctance torqueis produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an electromagnetic steel plate forming memberblanked in order to form a rotor core, which shows an embodiment of theinvention,

FIG. 2 is an enlarged front sectional view of a rotor to which theelectromagnetic steel plate forming member is applied, which shows astructure of the rotor,

FIG. 3 is a front sectional view of a main part of an IPM motor to whichthe rotor is applied, which represents schematically a positionalrelation of magnetic poles between a stator and the rotor which generatean optimum rotation torque,

FIG. 4A is a diagram for explaining the operation of the IPM motor,which is a schematic diagram showing the operation when the motorrotates normally,

FIG. 4B is a diagram for explaining the operation of the IPM motor,which is a diagram showing a relation between a current phase whichgenerates a rotating magnetic field of the motor and torque,

FIG. 5A is a diagram for explaining the operation of the IPM motor,which is a schematic diagram showing the operation when the motorrotates reversely,

FIG. 5B is a diagram for explaining the operation of the IPM motor,which is a diagram showing a relation between a current phase whichgenerates a rotating magnetic field of the motor and torque,

FIG. 6 is a front view of an electromagnetic steel plate forming memberblanked in order to mold a rotor core in a first related art,

FIG. 7 is a front sectional view of a part of an IPM motor to which therotor in the first related art is applied,

FIG. 8 is a front view of an electromagnetic steel plate forming memberblanked in order to mold a rotor core in a second related art,

FIG. 9 is a front sectional view of a part of an IPM motor to which therotor in the second related art is applied, which shows schematically apositional relation of poles between a stator and a rotor which generateoptimum rotating torque,

FIG. 10A is a diagram for explaining of the operation of the IPM motorin the second related art, which is a schematic diagram showing theoperation when the motor rotates normally, and

FIG. 10B is a diagram for explaining of the operation of the IPM motorin the second related art, which is a diagram showing a relation betweena current phase which generates a rotating magnetic field of the motorand torque.

DESCRIPTION OF THE EMBODIMENTS

According to a first aspect of the embodiment, a thin disc-shapedelectromagnetic steel plate forming member for forming a rotor coreincluding permanent magnets therein, wherein first and second magnetholes for inserting therein two magnets per pole are formed, in a rangeof radial pole pitch lines provided for the thin disc-shapedelectromagnetic steel plate forming member at a predetermined pole pitchangle, along a V-shape having a rotation center side as a vertex, thefirst and second magnet holes are partitioned by a center bridge locatedat a vertex portion of the V-shape, and one of the first and the secondmagnet holes is displaced in a direction apart from a center line ofpole pitch lines, and the other is displaced in a direction approachingto the center line of the pole pitch lines.

According to a second aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein the first and thesecond magnet holes have an asymmetrical shape.

According to a third aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein a length in a radiusdirection of one of the first and the second magnet holes is longer thana length in the radius direction of the other.

According to a fourth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein the first and thesecondmagnet holes are positioned so that a distance of an iron coreportion from an outer end surface of each hole to a circumferentialsurface of the thin disc-shaped electromagnetic steel plate formingmember is substantially the same.

According to a fifth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein arcuate spaces forpreventing flux leakage are provided, for both end portions in a radiusdirection of each of the first and the second magnet holes, in a bulgingshape toward an outer circumferential side.

According to a sixth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein arcuate spaces forpreventing flux leakage are provided, for both end portions in a radiusdirection of each of the first and the second magnet holes, in a bulgingshape toward an inner circumferential side.

According to a seventh aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein each of the firstand the second magnet holes includes an arcuate space for preventingflux leakage which bulges outward at a larger curvature than a curvatureof a corner portion of the magnet hole so as to include a cornerportion.

According to an eighth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein the first and thesecond magnet holes have a substantial rectangular.

According to a ninth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein the first and thesecond magnet holes have an arcuate.

According to a tenth aspect of the embodiment, the thin disc-shapedelectromagnetic steel plate forming member, wherein a cavity portion isprovided in an area of the thin disc-shaped electromagnetic steel plateforming member which is determined by stress limit by centrifugal forceand is located on the radial pole pitch line.

According to an eleventh aspect of the embodiment, an electromagneticsteel sheet laminator constituted in a block shape by laminating theplural thin disc-shaped electromagnetic steel plate forming member.

According to a twelfth aspect of the embodiment, A permanent magnet typesynchronous rotating electric machine rotor provides a rotor coreconstituted by the thin disc-shaped electromagnetic steel sheetlaminator, and a first and a second permanent magnets which are insertedinto a first magnet hole and a second magnet hole inside the rotor coreto generate fields.

According to a thirteenth aspect of the embodiment, the permanent magnettype synchronous rotating electric machine rotor, wherein in an ironcore portion formed between the outer end surfaces of the first and thesecond magnetic holes and a circumferential surface of the rotor core,magnetic fluxes formed by the first and the second permanent magnets aredistributed with displacement in the circumferential direction from acenter of radial pole pitch lines provided in the rotor core at apredetermined pole pitch angle.

According to a fourteenth aspect of the embodiment, the permanent magnettype synchronous rotating electric machine rotor, wherein the rotor is arotor of an 8-pole interior permanent magnet rotating electric machine.

According to a fifteenth aspect of the embodiment, a permanent magnettype synchronous rotating electric machine provides, and a statorarranged around the rotor.

According to a sixteenth aspect of the embodiment, the permanent magnettype synchronous rotating electric machine, wherein the number P ofmagnetic poles of permanent magnets arranged in magnet holes of therotor and the number M of salient magnetic poles arranged in salientpoles of the stator satisfies P=2(n+1) (n is an integer which is one ormore) and M=6P.

According to a seventeenth aspect of the embodiment, the permanentmagnet type synchronous rotating electric machine wherein the rotatingelectric machine is an interior permanent magnet rotating electricmachine in which the number of magnetic poles of the permanent magnetsis 8 poles.

According to an eighteenth aspect of the embodiment, a vehicle providesthe permanent magnet type synchronous rotating electric machine used asa drive motor for driving wheels.

According to a nineteenth aspect of the embodiment, a vehicle providesthe permanent magnet type synchronous rotating electric machine used asa generator.

According to a twentieth aspect of the embodiment, an elevator providesthe permanent magnet type synchronous rotating electric machine used asa drive motor.

According to a twenty-first aspect of the embodiment, a fluid machineprovides the permanent magnet type synchronous rotating electric machineas a drive motor.

According to a twenty-second aspect of the embodiment, a processingmachine provides the permanent magnet type synchronous rotating electricmachine used as a drive motor.

According to the embodiment, in the range of the radial pole pitch linesprovided in the rotor core at the predetermined pole pitch angle, one ofthe two magnet holes for inserting therein the two permanent magnets perpole along the V-shape is displaced in the direction apart from thecenter line of the pole pitch lines, and the other is displaced in thedirection approaching to the center line of the pole pitch lines.Hereby, the magnetic fluxes formed by the two permanent magnets aredistributed with displacement in the circumferential direction from thecenter of the pole pitch lines in the rotor core. Therefore, in the ironcore portion formed between the upper end surfaces of the two magnetholes arranged in the V-shape and the outer circumferential portion ofthe rotor core, saturation of the q-axis flux may be suppressed, andboth utilization of the reluctance torque and improvement of the magnettorque can be realized. As the result, the permanent magnet typesynchronous electric machine rotor and the permanent magnet typesynchronous electric machine can be realized, which may obtain largetorque also in the starting time and in abrupt change of load, are goodin efficiency, and are used in a field such as a vehicle, an elevator, afluid machine, a processing machine and the like.

Embodiment 1

FIG. 1 is a front view of an electromagnetic steel plate forming memberblanked in order to form a rotor core, which shows an embodiment of theinvention, and FIG. 2 is an enlarged front sectional view of a rotor towhich the electromagnetic steel plate forming member is applied, whichshows a structure of the rotor.

In FIG. 1, reference numeral 1 is an electromagnetic steel plate formingmember, 2 and 3 are first and second magnet holes, and 4 is an outerbridge. Further, in FIG. 2, reference numeral 5 is a center bridge, 6and 7 are first and second permanent magnets, 8 is a cavity portion, 10is a rotor, 11 is a rotor core, and 20, 21, 22, 23, 24, and 25 arearcuate spaces for preventing flux leakage. Reference character 0 is acenter of rotation, OP is a pole pitch line, OC is a center line of thepole pitch lines, 0 is a pole pitch angle, La and Lb are respectivelylengths in a radius direction of the first and second magnet holes 2 and3, and Cr is a distance of an iron core portion between the upper endsurface of the magnet hole 2, 3 and a circumferential surface of therotor core 11.

In FIG. 1, the electromagnetic steel plate forming member 1 is a thindisc-shaped electromagnetic steel plate for forming a rotor core. In aregion of radial pole pitch lines provided in this disc-shapedelectromagnetic steel plate forming member 1 at a predetermined polepitch angle, two magnet holes for inserting therein two magnets per poleare provided in the shape of V-shape having the rotation center side ofthe core as a vertex. The outer bridge 4 is located at a portion betweenthe outer end portion of the magnet hole 2, 3 of this electromagneticsteel plate forming member 1 and the outer circumferential portion ofthe rotor. Further, the center bridge 5 which partitions the magnetholes is provided in the electromagnetic steel plate forming member 1 soas to be located at the vertex portion of the V-shaped magnet holes 2,3. When the plural electromagnetic steel plate forming member 1 arelaminated in the block shape, an electromagnetic steel plate laminator(rotor core 11 in FIG. 1) is manufactured.

Next, in FIG. 2, characteristics of the first and second magnet holes 2,3 for inserting therein the two permanent magnets 6, 7 per pole in therotor core 11 formed of the electromagnetic steel plate forming member 1shown in FIG. 1 will be described in detail. In the region of the radialpole pitch lines OP provided along the V-shape having the rotationcenter side of the core 11 as a vertex at the predetermined pole pitchangle θ, the first magnet hole 2 is displaced in the direction apartfrom the center line OC passing through a center of the two pole pitchlines OP, and the second magnet hole 3 is displaced in the directionapproaching to the center line OC passing through a center of the twopole pitch lines OP.

These first and second magnet holes 2, 3 are arranged asymmetrically,and the length La in the radius direction of the first magnet hole 2 islonger than the length Lb in the radius direction of the second magnethole 3.

Further, the first and second magnet holes 2, 3 are provided in therotor core 11 in such positions that the distance Cr of the iron coreportion from the outer end surface of each hole for inserting thereinthe magnet 6, 7 to the outer circumferential portion of the rotor core11 is uniform.

Further, in the first and second magnet holes 2 , 3, at both endportions in the radius direction of the respective magnet holes, thearcuate spaces 20, 21, 22, and 23 for preventing flux leakage areprovided in the bulging shape toward the outer circumferential side orthe inner circumferential side.

Further, the arcuate spaces 24 and 25 are provided shape which isbulging outward at a curvature larger than a curvature of the cornerportion so as to include a corner portion of each of in the first andsecond magnet holes 2, 3 respectively. The first and second magnet holes2, 3 described in this embodiment may be formed in the substantiallyrectangular shape or alternatively arcuate.

Further, the cavity portion 8 is provided in an area determined bystress limit by centrifugal force and located on the radial pole pitchline OP in the rotor core 11 formed of the electromagnetic steel plateforming member 1.

Next, an IPMmotor to which the rotor according to the embodiment isapplied will be described.

FIG. 3 is a front sectional view of a main part of an IPM motor to whichthe rotor according to the embodiment is applied, which representsschematically a positional relation of magnetic poles between a statorand a rotor which generate an optimum rotation torque. The number ofmagnetic poles of permanent magnets of the rotor in FIG. 3 is eightpoles, and the number of magnetic poles of salient poles of the stator(it is equal to the number of slots) is 48 pieces. Combination of themagnet number and the slot number is the same as that in the secondrelated art.

In the IPM motor, permanent magnets 6, 7 embedded in a rotor 10 arearranged in the V-shape, and the same poles thereof face to each other.Though their thicknesses in the circumferential direction are the same,a length in the diameter direction of one permanent magnet 6 is longerthan the other permanent magnet 7. Further, distance Cr of an iron coreportion between the outer end surface of each permanent magnet and theouter circumferential portion of the rotor 10 is provided with the samedepth. Further, an open angle of the permanent magnets 6, 7 shown inFIG. 3 with respect to a rotation center of the rotor 10 is set to thesame angle as the open angle of the permanent magnets 55, 56 shown inFIG. 10 in the second related art. Accordingly, a repulsion-boundarypoint of magnetic fluxes by the permanent magnets in the outer iron coreportion sandwiched between the two permanent magnets 6 and 7 having thesame poles and the different length is located on the side of thepermanent magnet 7 which is short in length in the radius direction,that is, in a position 6-displacement in the circumferential directionfrom a center line Q-Q passing through a center of an opening angle(open angle) a of the permanent magnets 6, 7 arranged in the modifiedV-shape (on a center line OC of pole pitch lines of the rotor 10).

FIG. 3 shows the example in which the number of magnetic poles of thepermanent magnets arranged in the magnet holes of the rotor is 8 poles,and the number of salient magnetic poles arranged in salient poles(number of slots) of stator is 48 pieces. Preferably, this combinationis represented by the following relation.

P=2 (n+1) (n is an integer which is one or more), and M=6P, wherein P isthe number of magnetic poles of the permanent magnets in the rotor, andM is the number of magnetic poles of the salient poles of the stator.

By the combination thereof, a rotating electric machine which reducescogging and vibration, and operates at high output and with highefficiency may be obtained.

Next, an operation of normal rotation of rotating electric machine willbe described.

FIGS. 4A and 4B are diagrams for explaining the operation of the IPMmotor, which FIG. 4A is a schematic diagram showing the operation whenthe motor rotates normally, and FIG. 4B is a diagram showing a relationbetween a current phase which generates a rotating magnetic field of themotor and torque.

In FIG. 4A, a magnetic repulsion-boundary point of a d-axis in an outeriron core portion surrounded by the two same-pole permanent magnets 6, 7which are different from each other in length is on the surface of therotor 10 located on the outside of the bottom portion of theV-arrangement. In the following description, the amount of displacementon its surface is taken as a declination (δ) which is the amount ofdisplacement from the center line OC of the pole pitch lines OP by aboutone slot of the stator as shown in FIG. 3.

In case that poles formed by stator windings (not shown) attached in theslots 14 of the stator core 13 are as shown in FIG. 4A, on a gap surfacebetween the stator and the rotor, the left side of the magneticrepulsion-boundary point (existing on the line OC) becomes an attractiveportion in which the stator winding side is the N-pole and the permanentmagnet side is the S-pole, and the right side thereof becomes arepulsive portion in which both the stator winding side and thepermanent magnet side are the S-poles. Though the attractive portionbecomes dense in magnetic flux and the repulsive portion becomes sparsein magnetic flux, since the attractive portion is smaller in the numberof the N-poles on the stator side generated by the current direction ofthe stator windings is smaller than that in the related art exampleshown in FIG. 10, the attractive portion is higher in flux density thanthat in the example shown in FIG. 10. Further, since the repulsiveportion is larger in the number of the S-poles on the stator side thanthat in the example shown in FIG. 10, the repulsive portion is lower influx density than that in the example shown in FIG. 10. Since itsdifference of density is large, magnet torque which works on the rotorso as to move the rotor from the dense flux side to the sparse flux sidebecomes larger than that in the example shown in FIG. 10. Further, inFIG. 4A, though the open angle a of the two permanent magnets 6, 7 withrespect to the rotation center of the rotor is the same as that in theexample shown in FIG. 10, since the magnetic repulsion-boundary point inthe d-axis is displaced by about one slot (δ in FIGS. 3 and 4), thenumber of the magnetic poles of the salient poles (teeth) of the statoropposed to the salient pole of the rotor in which the q-axis flux flowsbecomes substantially two, while it is one in the example in FIG. 10.Therefore, magnetic saturation is difficult to occur. In the descriptionrelated to FIG. 3, since attraction occurs between the magnetic fieldsby the permanent magnets of the rotor and the rotating magnetic fieldsby the windings, and the d-axis salient pole portion of the rotor isattracted to the rotating magnetic fields by the windings, the fluxdensity in the portion shown by oblique lines in FIG. 4A becomesparticularly high. At this time, the N-pole component becomes furthershorter with respect to the S-pole component of the permanent magnetsand the S-pole component of the windings by one slot than that in theexample of FIG. 10, so that reluctance torque which is about to move therotor in the direction where the magnetic flux of the S-pole componentis shortened, that is, in the clockwise direction works more stronglythan that in the example of FIG. 10.

Next, a relation between current phase and torque of the permanentmagnet type synchronous rotating electric machine will be described.

As shown in FIG. 4A, in the iron core portion formed between the outerend surfaces of the first and second magnet holes 2, 3 and the outercircumferential portion of the rotor core 11, the magnetic fluxes formedby the first and second permanent magnets 6, 7 are distributed withdisplacement from the center line OC of the radial pole pitch lines OPprovided in the rotor core 11 at the predetermined pole pitch angle inthe circumferential direction of the rotor core 11. Accordingly, bydisplacing the d-axis flux, magnetic resistance of the d-axis becomeslarge, and the q-axis inductance Lq becomes increasingly larger than thed-axis inductance Ld. Therefore, since saliency becomes remarkable,reluctance torque is easy to generate. Simultaneously, in order tosuppress the q-axis flux saturation, the permanent magnet arrangement isdisplaced so that the number of the magnetic poles of the salient poles(teeth) of the stator opposed to the q-axis in the pole pitch lines OPis increased. Hereby, the saturation of the q-axis flux maybe mitigated.FIG. 4B shows a curve in a relation of the magnet torque generated bythe magnetic attraction and the magnetic repulsion between the magneticfields by the magnets and the rotating magnetic fields by the windings,and the reluctance torque generated by the attraction of the salientpole portion of the rotor to the rotatingmagnetic field by the winding.Therefore, an overall torque shown by a thick solid line in FIG. 4B maybe generated by putting the magnet torque and the reluctance torquetogether.

Next, an operation of reverse rotation of rotating electric machine willbe described.

FIGS. 5A and 5B are diagrams for explaining the operation of the IPMmotor, which FIG. 5A is a schematic diagram showing the operation whenthe motor rotates reversely, and FIG. 5B is a diagram showing a relationbetween a current phase which generates a rotating magnetic field of themotor and a torque.

FIG. 4 shows an optimum rotating torque position in case that therotating electric machine rotates clockwise (normally), while FIG. 5shows an optimum rotating torque position in case that the rotatingelectric machine rotates counterclockwise (reversely).

In FIG. 5A, the left side of the same-pole repulsion-boundary point ofthe d-axis of the rotor is a repulsive portion in which both the statorwinding side and the permanent magnet side are the S-poles. Further, theright side is an attractive portion in which the stator winding side isthe N-pole and the permanent magnets side is the S-pole. Herein,magnetic torque, which is about to move the rotor from the attractiveportion in which the flux density is dense to the repulsive portion inwhich the flux density is sparse, that is, in the counterclockwisedirection acts on the rotor. FIG. 5B shows the relation in this casebetween the current phase of the permanent magnet type synchronousrotating electric machine and the torque. Since overall torque isbasically the same as that in case of normal rotation of the rotatingelectric machine, it is omitted.

As shown in FIG. 3, of the two magnet holes 2, 3 for inserting thereinthe two permanent magnets 6, 7 per pole along the V-shape, which areprovided in the region of the radial pole pitch lines OP provided in therotor core 11 at the predetermined pole pitch angle θ, one magnet hole 2is displaced in a direction apart from the center line OC of the polepitch lines OP, and the other magnet hole 3 is displaced in a directionapproaching to the center line OC of the pole pitch lines OP. Hereby,since the magnetic fluxes formed by the two permanent magnets 6,7 aredistributed with displacement from the center line OC of the pole pitchlines OP in the rotor core 11 in the circumferential direction, both themagnet torque and the reluctance torque in the V-arrangement of thepermanent magnets of which lengths in the radius direction are differentimprove with respect to the one-rotating direction, and efficiency ofthe permanent magnet type synchronous rotating electric machine may beincreased, compared with the rotor in which the permanent magnetsembedded in the rotor are arranged in isosceles V-shape as described inthe second related art shown in FIG. 10. The improvement of the magnettorque with respect to the one-rotating direction may improve greatlyefficiency of the permanent magnet type synchronous rotating electricmachine in a low-speed at light load area where the current is low.

Further, generally, centrifugal force acts on the embedded permanentmagnet by the rotation of the rotor 10, so that the permanent magnet isabout to go to the outer circumferential side of the rotor. The largerthe contact area between the permanent magnet and the permanent magnetinsertion hole is, the closer to the rotation center the permanentmagnet is located, and the lighter the weight of the permanent magnetis, the stronger the centrifugal force becomes. In the V-arrangement ofthe permanent magnets in which one of the two permanent magnets 6, 7 isshort in length in the radius direction and the other is long in lengthas in the embodiment, the permanent magnet 7 which is shorter than thepermanent magnet 6 in length in the radius direction is setting up withrespect to the rotation center but light in weight correspondingly tothe short length. The permanent magnet 6 which is long er than thepermanent magnet 7 in length in the radius direction, since it islocated closer to the horizontal with respect to the rotation center onconstruction than that in the isosceles V-shape, is strong incentrifugal force.

Further, as shown in FIG. 2, on the construction, the arcuate spaces 20to 23 for preventing flux leakage are provided for the both end portionsof each of the first and second magnet holes 2, 3 in the bulging shapetoward the outer circumferential side or the inner circumferential side.Further, the first and secondmagnet holes 2, 3 are provided respectivelywith the arcuate spaces 24, for preventing flux leakage which bulgetoward the outer circumferential side at a curvature larger than acurvature of the corner portion so as to include the corner portion ofeach magnet hole. Therefore, by these arcuate spaces, concentration ofstress in the magnet holes in the rotor 10 may be diffused andmitigated.

Further, as shown in FIG. 2, under the constitution of the embodiment,since the magnet holes 2, 3 for inserting therein the two magnets perpole are provided in the rotor core 11 along the V-shape and the centerbridge 5 is provided between the magnets holes 2,3, the centrifugalforce-resistance increases more by this center bridge. Namely,high-speed rotation is realized.

Further, as shown in FIG. 2, since the eight cavity portions 8 areformed in the rotor core 11, the weight of the rotor 10 which is bynature a weight may be reduced correspondingly, so that mechanical lossin a bearing portion (not shown) which supports a rotor shaft (notshown) fitted into a hollow portion of the rotor 10 may be reduced, andefficiency may be increased. In this case, the cavity portion 8 islocated and formed in the area set by shape and dimension determined bystress limit which generates by the centrifugal force acting on therotor 10 and by shape and dimension determined by judging the locationwhere the influence on a magnetic path is small. Therefore, themechanical strength for the centrifugal force of rotation is notimpaired, the flow of fluxes (magnetic path) by the stator winding (notshown) attached to the slot 14 of the stator 12 and by the permanentmagnets 6, 7 of the rotor 10 is not obstructed, and a bad influence isnot exerted upon characteristics.

Further, since coolant may be taken in the cavity portion 8 of the rotorcore 11 and circulated, the rotor core may be directly cooled, so thatcooling property of the rotor 10 may be improved.

Thus, in the description of the principle in FIG. 3, the d-axis magneticrepulsion-boundary point provided for the rotor is displaced to theshorter permanent magnet side by one slot, while in the second relatedart shown in FIG. 10, the d-axis magnetic repulsion boundary point isnecessarily located in the center of the usual isosceles V-shapedpermanent magnet arrangement. The amount of this displacement isappropriately different according to combination of the slot number ofthe stator of the rotating electric machine and the pole number of therotor.

Further, though the so-called slot stator has been described in theabove description of the embodiment and the figures, since theembodiment of the invention relates to the structure of the rotor, thestator is not limited to the slot stator, a so-called slot-less statormay be used. Also in this case, the similar advantage may be obtained.

Further, the invention maybe applied also to a linear motor whichlinearly moves in place of the rotating motor.

According to the electromagnetic steel plate forming member, theelectromagnetic steel plate laminator, the permanent magnet typesynchronous rotating electric machine rotor provided this, and thepermanent magnet type synchronous rotating electric machine of theembodiment, in the iron core portion formed between the upper endsurfaces of the two magnet holes arranged in the V-shape in the rotorcore and the outer circumferential portion of the rotor core, thesaturation of the q-axis flux maybe suppressed, and both utilization ofthe reluctance torque and improvement of the magnet torque can berealized. In result, since large torque maybe obtained also in thestarting time and in abrupt change of load, efficiency can be made good.Therefore, the embodiment of the invention is effective as a drive motoror a generator for a hybrid car, a fuel cell car, or an electric car, asa drive motor or a generator for a railway vehicle, and as a generatorused in a generator car for an uninterruptible power supply. Further,the embodiment of the invention is effective also as a drive motor foran industrial machine such as an elevator, an elevator in a multi-levelparking zone, a compressor or a blower for wind or water power, a fluidmachine such as a pump, or a working machine including mainly asemiconductor manufacturing apparatus or a machine tool.

1. A permanent magnet synchronous rotating electric machine comprising:a rotor comprising: a first hole; a second hole provided on an oppositeside with respect to a center line extending along a radial direction ofthe rotor; a first magnet provided in the first hole and extending alonga first longitudinal axis inclined at a first acute angle with respectto the center line; and a second magnet provided in the second hole andextending along a second longitudinal axis inclined at a second acuteangle with respect to the center line, the second acute angle beingsmaller than the first acute angle and being formed opposite to thefirst acute angle with respect to the center line, an outercircumferential distance between a first radially outer end of the firstmagnet and a second radially outer end of the second magnet beinggreater than an inner circumferential distance between a first radiallyinner end of the first magnet and a second radially inner end of thesecond magnet; and a stator including a stator core and a stator windingprovided to the stator core, the stator having a displacement point ofmagnetism to be generated by a current passing through the statorwinding, the displacement point being provided on an inner peripheralsurface facing an outer peripheral surface of the rotor via a gap, themagnetism of the rotor on the outer peripheral surface being differentfrom the magnetism of the stator on the inner peripheral surface on afirst side of the center line when the displacement point is providedsubstantially on the center line of the rotor, the magnetism of therotor on the outer peripheral surface being same as the magnetism of thestator on the inner peripheral surface on a second side of the centerline when the displacement point is provided substantially on the centerline of the rotor, the second side being provided on an opposite side ofthe first side with respect to the center line in the circumferentialdirection.
 2. The permanent magnet synchronous rotating electric machineaccording to claim 1, wherein the rotor includes a first pole pitch lineand a second pole pitch line, the first and second pole pitch linesextending along the radial direction, the first and second magnets beingprovided between the first and second pole pitch lines in thecircumferential direction, the center line forming a bisector of thefirst and second pole pitch lines, and wherein no magnets are providedbetween the first and second pole pitch lines in the circumferentialdirection other than the first and second magnets.
 3. The permanentmagnet synchronous rotating electric machine according to claim 1,wherein the first magnet is provided in front of the second magnet in anormal rotating direction of the rotor.
 4. The permanent magnetsynchronous rotating electric machine according to claim 1, wherein therotor further comprises a center bridge provided on the center line andbetween the radially inner ends of the first and second magnets.
 5. Thepermanent magnet synchronous rotating electric machine according toclaim 1, wherein a length of the first magnet along the firstlongitudinal axis is longer than a length of the second magnet along thesecond longitudinal axis.
 6. The permanent magnet synchronous rotatingelectric machine according to claim 1, wherein the first and secondmagnets are provided to form a substantially v-shape.
 7. The permanentmagnet synchronous rotating electric machine according to claim 1,wherein the rotor includes a first pole pitch line and a second polepitch line, the first and second pole pitch lines extending along theradial direction, the first and second magnets being provided betweenthe first and second pole pitch lines in the circumferential direction,the center line forming a bisector of the first and second pole pitchlines, wherein no magnets are provided between the first magnet and thesecond pole pitch line in the circumferential direction other than thesecond magnet, and wherein no magnets are provided between the secondmagnet and the first pole pitch line in an opposite circumferentialdirection other than the first magnet.
 8. A permanent magnet synchronousrotating electric machine comprising: a rotor comprising: a first hole;a second hole provided on an opposite side with respect to a center lineextending along a radial direction of the rotor; a first magnet providedin the first hole and extending along a first longitudinal axis inclinedat a first acute angle with respect to the center line extending along aradial direction of the rotor; and a second magnet provided in thesecond hole and extending along a second longitudinal axis inclined at asecond acute angle with respect to the center line, the second acuteangle being smaller than the first acute angle and being formed oppositeto the first acute angle with respect to the center line, an outercircumferential distance between a first radially outer end of the firstmagnet and a second radially outer end of the second magnet beinggreater than an inner circumferential distance between a first radiallyinner end of the first magnet and a second radially inner end of thesecond magnet; and a stator including a stator core and a statorwinding, the stator core having a plurality of teeth, the stator windingbeing provided to the teeth, the stator having a displacement point ofmagnetism to be generated by a current passing through the statorwinding of the stator, the second displacement point being provided onan inner peripheral surface facing an outer peripheral surface of therotor via a gap, a d-axis being defined as a magnetic axis of a magneticconvex portion of the rotor, a q-axis being defined as a salient pole ofa magnetic concave portion of the stator, substantially two of the teethof the stator core being opposed to the salient pole in which magneticflux along the q-axis flows when the displacement point is providedsubstantially on the center line of the rotor.
 9. The permanent magnetsynchronous rotating electric machine according to claim 8, wherein therotor includes a first pole pitch line and a second pole pitch line, thefirst and second pole pitch lines extending along the radial direction,the first and second magnets being provided between the first and secondpole pitch lines in the circumferential direction, the center lineforming a bisector of the first and second pole pitch lines, and whereinno magnets are provided between the first and second pole pitch lines inthe circumferential direction other than the first and second magnets.10. The permanent magnet synchronous rotating electric machine accordingto claim 8, wherein the first magnet is provided in front of the secondmagnet in a normal rotating direction of the rotor.
 11. The permanentmagnet synchronous rotating electric machine according to claim 8,wherein the rotor further comprises a center bridge provided on thecenter line and between the radially inner ends of the first and secondmagnets.
 12. The permanent magnet synchronous rotating electric machineaccording to claim 8, wherein a length of the first magnet along thefirst longitudinal axis is longer than a length of the second magnetalong the second longitudinal axis.
 13. The permanent magnet synchronousrotating electric machine according to claim 8, wherein the first andsecond magnets are provided to form a substantially v-shape.
 14. Thepermanent magnet synchronous rotating electric machine according toclaim 8, wherein the rotor includes a first pole pitch line and a secondpole pitch line, the first and second pole pitch lines extending alongthe radial direction, the first and second magnets being providedbetween the first and second pole pitch lines in the circumferentialdirection, the center line forming a bisector of the first and secondpole pitch lines, wherein no magnets are provided between the firstmagnet and the second pole pitch line in the circumferential directionother than the second magnet, and wherein no magnets are providedbetween the second magnet and the first pole pitch line in an oppositecircumferential direction other than the first magnet.
 15. A rotor corecomprising: an electromagnetic steel plate layered body comprising: afirst hole; and a second hole provided on an opposite side with respectto a center line extending along a radial direction of the rotor; afirst magnet provided in the first hole and extending along a firstlongitudinal axis inclined at a first acute angle with respect to thecenter line; and a second magnet provided in the second hole andextending along a second longitudinal axis inclined at a second acuteangle with respect to the center line, the second acute angle beingformed opposite to the first acute angle with respect to the centerline, an outer circumferential distance between a first radially outerend of the first magnet and a second radially outer end of the secondmagnet being greater than an inner circumferential distance between afirst radially inner end of the first magnet and a second radially innerend of the second magnet, the second acute angle being smaller than thefirst acute angle so that saturation of flux along q-axis is suppressedand reluctance torque is produced.
 16. The rotor core according to claim15, further comprising: a first pole pitch line extending along theradial direction; and a second pole pitch line extending along theradial direction, the first and second magnets being provided betweenthe first and second pole pitch lines in the circumferential direction,the center line forming a bisector of the first and second pole pitchlines, wherein no magnets are provided between the first and second polepitch lines in the circumferential direction other than the first andsecond magnets.
 17. The rotor core according to claim 15, wherein thefirst magnet is provided in front of the second magnet in a normalrotating direction of the rotor core.
 18. The rotor core according toclaim 15, wherein the rotor core includes a center bridge provided onthe center line and between the radially inner ends of the first andsecond magnets.
 19. The rotor core according to claim 15, wherein alength of the first magnet along the first longitudinal axis is longerthan a length of the second magnet along the second longitudinal axis.20. The rotor core according to claim 15, wherein the first and secondmagnets are provided to form a substantially v-shape.
 21. The rotor coreaccording to claim 15, further comprising: a first pole pitch lineextending along the radial direction; and a second pole pitch lineextending along the radial direction, the first and second magnets beingprovided between the first and second pole pitch lines in thecircumferential direction, the center line forming a bisector of thefirst and second pole pitch lines, wherein no magnets are providedbetween the first magnet and the second pole pitch line in thecircumferential direction other than the second magnet, and wherein nomagnets are provided between the second magnet and the first pole pitchline in an opposite circumferential direction other than the firstmagnet.